Photo as well as laser transistors are known. A new application for an avalanche phototransistor, specifically operated as an optical comparator, is described in the journal IEEE TRANSACTIONS ON ELECTRON DEVICES, Vol. ED-30, No. 4, April 1983, pages 408 to 411. The operating principle of an InGaAsP/InP laser transistor is, for example, known from the publication in Appl. Phys. Lett. 47(7), Oct. 1, 1985, Pages 649 to 651.
With increasing miniaturization in the field of optoelectronics it is desirable to build complex microsystems consisting of sensing, logic and actuating elements, in largely an integrated form. Thus, for example, integrated optical elements are known, in which a phototransistor is combined with an InGaAsP/InP hetero-junction with a luminescent diode (LED) (JOURNAL OF LIGHTWAVE TECHNOLOGY, Vol. LT 3, No. 6, December 1985, pages 1264 to 1269).
Furthermore, semiconductor elements for processing optical data signals with respect to amplitude and pulse duration, so-called optical repeaters, are known, specifically in the form of hybrid repeaters or in the form of an optoelectronically integrated repeater, with several semiconductor elements such as, for example, a photodiode, transistors, a laser diode, being monolithically integrated.